Straw cups are very popular, and known straw cups typically include a container, a lid assembly selectively attachable to the container, and a straw assembly selectively attachable to the lid assembly. Often, the lid assembly is adapted to move the straw assembly between an operative position wherein the straw assembly is positioned for a user to drink from the cup, and a stowed position wherein the straw assembly is at least partially enclosed by the lid assembly and unavailable for the user to drink from the cup.
When liquid is withdrawn from the container, through the straw, a negative pressure may be created within the container, thus making it more difficult to further withdraw liquid. To address this problem, various types of vents have been used to allow air into the container and equalize the pressure between the inside of the container and the outside atmosphere. In addition to equalizing the relative pressure within a container, it may also be desirable to prevent liquid from escaping the container through the vent, if the cup is tilted or knocked over. It would be beneficial to provide a vented closure for a cup that allowed pressure equalizing air to enter the container and restricted unwanted outward flow of liquid from the container.